Phthalocyanine Gas Sensor Of Thin Film Materials Developed And Its Characteristics Of Study

As a new type of sensor, gas sensor developed very quickly today. The thin film materials have a particular microstructure, wonderful physical and chemical properties, excellent surface character, which make the thin film technology become the key of the gas sensor technique. Metal phthalocyanine (MPc) and their derivatives are organic materials of P-type semiconductor having the thermal/chemical stability. Due to the phthalocyanine framework we can change the central metal ion or introduce function substituted groups such as alkyl or alkoxy into the peripheral positions or the axis. It has special properties including optic, electric, acoustic, calorific, magnetic and chemical and so on via modulating its composition of the molecule.The gas sensing mechanism of phthalocyanines and influence of thin film structure and substitutes on gas-sensitivity were illustrated in this paper. The results have showed the gas sensing characteristic was dependent on the self-structure and the morphology of the films. We studied the synthetic method of phthalocyanine. Using solvent to synthesis metallophthalocyanines by benzene bitter wine-urea law, a sensitive film was grown on interdignit electrodes by vacuum sublimation after the purification. The crystal structures of the phthalocyanine films were characterized with XRD and FT-IR. The analysis of SEM shape indicated that the size of the film particles was equalized. We also found that metallophthalocyanine mainly has two adsorption bands through UV-visible absorption spectrum. One is Q band at 600~800nm, the other one is B band at 250~350nm. The adsorption spectrum will Einstein shift after the phthalocyanine film was annealed. It demonstrated the crystal form changed fromα-form toβ-form.The structure and technological process of gas sensor were simulated and optimized using the Intellisuite software. An integrated thin-film gas sensor was realized by technologies of microelectro-mechanical systems (MEMS). The work principle of gas sensor was discussed theoretically. Meanwhile, we tested and analyzed the sensing materials of gas sensor. The testing results indicated that the metal phthalocyanine sensing films could exhibit the optimal sensing characteristic when the gas sensor worked at room temperature or low temperature. The sensing films had excellent selectivity to oxidation gas NO2. Current will increase with the concentration of the gas increasing which was identical with the rules that the oxidation gas NO2 adsorbed on the P-type semiconductor. Copper phthalocyanine sensing films had fast response rate to NO2. When the concentration of the gas was 160ppm, the response time was 6s and the recovery time was 15s. Before and after annealing the response time of the nickle phthalocyanie thin films were 13s and 1.8min to the 65ppm NO2 respectively. The reducing gases such as H2, NH3 and CO had similar current-concentration change rules which was opposite with the ones of the oxidation gas NO2.